Implantable medical devices, such as electrical stimulators or therapeutic agent delivery devices, may be used to deliver electrical stimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, mood disorders (e.g., depression), other psychiatric disorders (e.g., obsessive-compulsive disorder), gastroparesis or diabetes. In some cases, the electrical stimulation may be used to stimulate muscles, e.g., functional electrical stimulation (FES) to promote muscle movement or prevent atrophy. In the case of an electrical stimulation therapy system, an implantable medical device may deliver electrical stimulation therapy via one or more leads that include electrodes located proximate to a target tissue site, which may be proximate to the spinal cord, pelvic nerves, peripheral nerves, the stomach or other gastrointestinal organs or within the brain of a patient. Alternatively, electrical stimulation may be delivered by one or more electrodes associated with a leadless stimulator.
During a programming session, which may occur during implant of the medical device, during a trial session, or during a follow-up session after the medical device is implanted in the patient, a clinician may select therapy parameter values for the medical device that provide efficacious therapy to the patient. In the case of electrical stimulation delivered in the form of pulses, the therapy parameters may include an electrode combination (i.e., particular electrodes selected from an array of electrodes and the polarities of the selected electrodes), an amplitude, which may be a current or voltage amplitude, a pulse width, and a pulse rate for stimulation signals. In some cases, such as in current-based electrical stimulation systems, electrodes may be identified as source or sink electrodes. A group of therapy parameter values may be referred to as a program in the sense that they drive the stimulation therapy to be delivered to the patient.